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1==============2Audio Clocking3==============4 5This text describes the audio clocking terms in ASoC and digital audio in6general. Note: Audio clocking can be complex!7 8 9Master Clock10------------11 12Every audio subsystem is driven by a master clock (sometimes referred to as MCLK13or SYSCLK). This audio master clock can be derived from a number of sources14(e.g. crystal, PLL, CPU clock) and is responsible for producing the correct15audio playback and capture sample rates.16 17Some master clocks (e.g. PLLs and CPU based clocks) are configurable in that18their speed can be altered by software (depending on the system use and to save19power). Other master clocks are fixed at a set frequency (i.e. crystals).20 21 22DAI Clocks23----------24The Digital Audio Interface is usually driven by a Bit Clock (often referred to25as BCLK). This clock is used to drive the digital audio data across the link26between the codec and CPU.27 28The DAI also has a frame clock to signal the start of each audio frame. This29clock is sometimes referred to as LRC (left right clock) or FRAME. This clock30runs at exactly the sample rate (LRC = Rate).31 32Bit Clock can be generated as follows:-33 34- BCLK = MCLK / x, or35- BCLK = LRC * x, or36- BCLK = LRC * Channels * Word Size37 38This relationship depends on the codec or SoC CPU in particular. In general39it is best to configure BCLK to the lowest possible speed (depending on your40rate, number of channels and word size) to save on power.41 42It is also desirable to use the codec (if possible) to drive (or master) the43audio clocks as it usually gives more accurate sample rates than the CPU.44 45 46 47